In recent years, a straddle electric vehicle which incorporates an electric motor as a driving power source has been developed. In an electric motorcycle which is an example of the straddle electric vehicle, it is necessary to incorporate a battery for supplying electric power to the electric motor. A certain electric motorcycle incorporates a low-voltage battery for activating auxiliary machines in addition to a high-voltage battery for storing the electric power supplied to the electric motor to activate the electric motor (see, e.g., Patent Literature 1).